Furnace for annealing metal sheets by a continuous process



Jan; 30, 1934. E. GRIFFITHS 1,944,974

FURNACE FOR ANNEALING METAL SHEETS BY A CONTINUOUS PROCESS Filed May 12, 195o 7 sheets-sheet y1 @im M @Q E. GRIFFITHS 1,944,974

FURNACE FOR ANNEALING METAL SHEETS BYl A CONTINUOUS PROCESS Jan. 30, 1934.

u D D D 3 D U D D D J u D D l D 3p .tu a I Jan. 30, 1934o E, GR|FF|THS 1,944,974

FURNACE FOR ANNEALING METAL SHEETS BY A CONTINUOUS PROCESS Filed May l2, 1930 7 Sheets-Sheet 3 j WQ? 7 73 y M n t f4@ /f Mea/Maf@ Jan. 30, 1934. E;l GRlFFlTHS 1,944,974

FURNACE FOR ANNEALING METAL SHEETS BY A CONTINUOUS PROCESS Filed May 12, 1950 7 Sheets-Sheet 4 64S@ Q d Q gall E. GRIFFITHS Jan. 30, 1934.

FURNACE FOR ANNEALING METAL SHEETS BY A CONTINUOUS PROCESS Filed May 12, 1930 7 Sheets-Sheet 5 E. GRIFFITHS Jan. 3o, 1934. 1,944,974

y FURNACE FOR ANNEALING METAL SHEETS BY A CONTINUOUS PROCESS '7 sheets-sheet 6 Filed May 12; 1930 29M di 9% Jan. 30, 1934.

FURNACE FOR ANNEALING METAL SHEETS BY A CONTINUOUS PROCESS Filed May 12, 1930 '7 Sheets-Sheet 7 E. GRIFFITHS 1,944,974

Patented Jan. 59, 1934 l,9fl4,974

FICE

FR. ANNEALENG METAL SHEETS BY A CN'llNUUS PROCESS Ernest Grilths, Liverpool, England 6 Claims.

This invention relates to furnaces for annealing metal sheets by a continuous process, and although generally applicable to such furnaces is specially applicable to furnaces in which, as described in patent application No. 324,675 dated July 31st 1928, made by the present applicant and another; the sheets are passed through the furnace by conveying means which support the sheets by their top edges so that the sheets hang vertically either in line or with their planes obliquely disposed at a sinall angle to the direction of motion; and the invention comprises iinprc-vernents in the construction of furnace, burners and ilues, whereby hot gases supplied through a plurality of burners are efhciently applied to the line of travelling sheets supported by their top edges, said hot gases in one niodication afterwards passing through a recuperator in which heat is transferred from the products 29 of combustion to the air employed in the burners,

and whereby the ends of the furnaces are practcally closed by means which permit the entrance and exit of the sheets without substantial, admission or escape of gases, a similar arrangement being employed in the cooling chamber.

According to the invention the fuel inlets for burners and the outlets for the products of cornbustion are so arranged that the high temperature gases flow from inlet to outlet in a direction sub- 30 stantially transverse to the length of the furnace,

and parallellwith, and on each side of the vertical sheets to be heated, so that the full length of each side of the said sheet as it is propelled lo-ngitudinally through the furnace, moves at right angles to and in contact with the said transverse flow of the gases.

In the preferred form the fuel inlets are arranged in two groups at the bottom of the furnace and at opposite sides, the exhaust outlets being arranged at the bottom but at a lower level than the inlets; in a inodication the fuel inlets may be arranged at the top and the outlets at the bottom, or a fuel inlet or inlets may be at the bottoni and the outlets be located at each side of the top; or the fuel inlets and outlets may respectively be arranged on opposite sides of the top, or at the sides at different heights.

Preferably there is combined with the furnace a recuperator, the opposite sides of the heat eX- changing surfaces of which are in contact, respectively, with the products of combustion from the furnaces, and the air which is mixed with the fuel gas in the furnace. This permits the ow of gases described to be utilized without undue loss of elioiency.

The preferred form of recuperator employed is that comprised of hollow bricks having longitudinal airways cored through thern, the bricks being arranged in tiers so as to provide vertical airways for the air, and horizontal passageways, sub-divided by tiles, through which the products of combustion pass.

In the preferred arrangement a pair of main fuel inlet flues are arranged longitudinally, one on each side of the centre line of the furnace, upcasts being led from the said fiues to several mixing chambers longitudinally disposed on each side of the said centre line, said mixing chambers being also provided with upcasts leading from the hot air ilue of a recuperator, and means for regulating the flow through the two upcasts; laterally disposed inlets or burners connecting the several mixing chambers to the lower part of the interior of the furnace, are arranged on opposite sides of the centre line; and an exhaust flue and inlets from the bottom of the furnace to the said flue are arranged longitudinally along the centre line of the furnace.

The inlets from the mixing chambers to the furnace are preferably severally located at the bot-torn of respective ilue recesses, the outer walls of which taper inwardly so as to direct the hot gases inwardly as they rise vertically.

Preferably the main fuel inlets and outlets are located in the central portion of the furnace, the end portions, in which the temperature desired is usually less than that of the central part of the furnace, being provided with regulable au'riiliary outlets.

The doors of the outlet end of the furnace are preferably constructed in two parts each pivoted on a vertical pivot, the pivots being arranged some distance apart and in rear of the edges of the door; the abutting edges of the doors being obliquely arranged and the planes of the doors intersecting at an acute angle.

There is combined with the furnace a cooling chamber provided with two pairs of exit doors preferably having oblique edges as described, the space between the pairs of doors communicating with exhaust means.

The sheets are attached to depending portions of an endless conveyor after the manner described in the specification above mentioned, and the conveyor is located in a recess, the base of which is carried after the manner of a cantilever froin one of the walls of the furnace, said depending portions being detachably secured to canti-lever elements of the conveyor supported by a longitudinal guide located near the edge of the longitudinal opening below the roof of the furnace through which the attachment parts depend.

The invention also includes details of construction as hereinafter descrised and claimed.

I have illustrated iny invention as applied to an annealing furnace for steel sheets, in 'the accompanying drawings, in whiohg Figs. 1 and 1A taken together forni an elevation in longitudinal medial section.

Figs. 2 and 2A forming a corresponding plan in conventional transverse section.

Fig. 3 is a transverse section, the leftehand half being in section on the line Ill-ll and the righthand half being in section on the line IHl'f of Fig. l.

Figs. Ll, 5 and 5A being transverse sections on the line V-IV, V-V and lf3-Ve of Fig. 2A.

Fig. 6 is a longitudinal elevation similar to l but in section on the line vl-NI of Fig. 3.

Figs. 7, S and 9 illustrate the preferred form of conveyor.

Fig. 7 being a fragmentary elevation.

Fig. 8 a transverse section; and

Fig. 9 a fragmentary plan; and

Figs. l0, ll and l2, are views of modications, and

Fig. 13 is a detail View of the preferred form of recuperator.

Fig. 14 is a fragmentary View similar to the upper part of Fig. 3 and shows a modification.

A is the furnace chamber thr ugh which the sheets S attached to the conveyor, pass in vertical line in succession, and its transverse dimension is made a minimum consistent with a substantial area for the passage of the flue gases on each of the sheet; al are the vertical side walls, ai. are tapering recesses up which the-hot gases flow, a3 is the floor of the furnace, all a longitudinal opening under the roof of the furnace to accomn modate the depending portions of the conveyor; a5 is a recess to take the conveyor, the base of which recess forms a canti-lever extension from the walls of the furnace, a6 are detachable roof segments which close the recess a5 and conveyor opening all, the segments being provided with lifting portions c7 by which the roof segments are adapted to be raised with lifting tackle carried from cross beams a8 supported by the main columns a9 the chain portion of the conveyor passes round two chain wheels one of which bl only shown; the part of the conveyor passing through the furnace being located in the recess d5 and the outside portion being guided by suitable guides carried from the columns a9.

The front end of the furnace is closed by a pair of vertical contact rollers C, the rollers and the casings carrying them no 1mally closing the inlet end of the furnace with the exception of a space for the conveyor, the sheets vertically carried by the conveyor passing in between the rollers which are fitted with springs to p'ess them together. The rear end of the furnace is closed by doors D the abutting edges of which are arranged oblique- 1y, the doors are carried by vertical pivots dl arranged some distance apart on opposite sides of the centre line, the abutting edges d2 of the doors are oblige-.ely disposed sloping outwardly and downwardly, the planes of the doors when closed intersecting at an acute the sheet emerges from the furnace the upper portion of its vertical leading edge, that is to the part of the said edge nearest the point of support from the conveyor, engages the upper portion of the obliqucly disposed edges 0f the doors, the sheet gradually emerging, and said leading edge making successive point contacts with the obliquely disposed edges of the doors.

The doors are preferably maintained open by the small amount necessary to allow the sheets to pass; the oblique edges are set at such an angle that when the lower end of the leading vertical edge of the sheet passes the lower part of the edge of the door, the top edge of each of the doors or an extension thereof is in contact with the plane of the sheet; the two oblique edges of the doors thus form oblique lateral supports to prevent deformation of the sheet. The edges of the doors may be continued forwardly as vertical planes in Contact with the sheet. The pivots are preferably in rear of the edges of the doors.

ln the example illustrated, the sheets pass directly from the furnace doors D into a cooling chamber il. at the exit end of which two such doors D are preferably fitted, the space between the two doors being connected by means which exhaust the gas therefrom, so that atmospheric air enters the said by any leakage openings and in this way prevents the pollution the atmosphere by gas escaping from the cooling chamber.

G is the main fuel gas supply pipe which is tted with two vertical down pipes gl which lead by the respective oasings g2 into respective main fines g3 (see Fig. 3) one located on each side of the centre line of the furnace and below the bottom thereof, the main flue is fitted with upcasts gli each upcast opening into a mixing charnber F, each upcast being fitted with a regulating tile g5 operated through a regulating box o6.

K is the exhaust flue and icl the exhaust outlets leading froro the bottoni of the furnace to the said flue, the flue F; communicates through the flues k2 (see Fig. l) with the inlet to a recuperator H consisting vof tiers of bricks hl having cavities h2 which form vertical passageways for the upward flow of the air for combustion which enters at J, and after passing through the cavities of the bricks passes to the hot air flue jl, the exhaust gas passing through channels formed between the bricks by tiles h3 so as to give a multiple reverse flow between the ues k2, k3 and kll, the latter leading to the chimney. Y

The vertical arrangement of the air passages in the recuperator bricks is of considerably advantage since a positive pressure of the air is obtained by thermostatic action which pressure assits in mixing and obviates the need of a fan or the lille with its attendant losses and leakages.

The hot air flue :il communicates with each of the mixing chambers F byrnean's of a pair of upcasts 9'2 (see left-hand side 3) the flow of air being controlled by regulating tiles 7'3 and boxes 'll, a suitable mixture of air and fuel gas passes from the respective mixing boxes through inlet fl or burners fl to the bottoni portions of the furnace, the inlets being preferably some distance above the door a3 of the furnace.

The inlets fl are respectively arranged at the bottom of the flue recesses o2 so that the flame and hot gas resulting from the combustion as they flow upwardly are deflected inwardly by the all; on reaching the top of the furnace the two streams of gas are deflected downwardly in contact respectively with the opposite sides of the sheets, and pass through the exhaust outlets k1 to the exahust flue and thence through the reouperator as described.

The fuel inlets ,fl and the exhaust oulets kl of which there are four sets in the example illustrated, are grouped in the central portions 1ongitudinally of the furnace, in order that the required temperature may be maintained in the end portions of the furnace, and said portions are fitted with auxiliary exhaust outlets k (see end portions of Fig. l) which open into ues k6 and k6 communicating respectively through the ilues k7 with the exhaust flues k2 and k3; these auxiliary exhaust flues are tted with regulating tiles and boxes lc9 by which the extent to which the hot gases are drawn from the fuel inlets to the end portions of the furnace may be regulated.

The cooling chamber is constructed in sections e1 and the upper portion is arranged so as to have an opening such as a4 and a recess a5 to take the conveyor; the conveyor is carried beyond the outlet of the cooling chamber a sufiicient distance to permit the convenient detachment of the sheets. The preferred form of conveyor is shown in Figs. 7, 8 and 9 ;-B are the depending bars which are fitted with any suitable means for gripping the upper edges of the sheets under treatment, preferably one of the arrangements described in the above mentioned specification.

In the arrangement shown the folded over edge of the sheets S is supported by the hooked end b1 of a detachable part b2 secured to the depending part B; the said folded edge being held in place by cam-shaped clamps b3 pivotally attached to the bar B and operated to release by suitable cams engaging pins on the arm b4. Each depending part B is detachably secured to a canti-lever element b5 having a V-shaped saddle piece 196 guided by a main longitudinal guide b'l secured in position on the base 128 by the clamp b9. The part b5 is bolted to one of the links of chain conveyor b10, the links of which are located immediately over the guide b7, the turning movement of the canti-lever element b5 being prevented bythe slide jaw bll xed to the tail end of the canti-lever piece and engaging an auxiliary guide Z212.

Fig. 8 shows the parts of the conveyor gear and the recess over the furnace; the ends of the conveyor as stated pass overv chain wheels, the return or unloaded side of the conveyor being guided by guides after the manner shown in Fig. 8.

The state of the sheets as they pass through the furnace is observed through sight holes and the furnace is fitted with the usual accessories employed in working such furnaces.

Instead of carrying the conveyor from the base of a chamber carried by a side wall as shown in Fig. 8, the arrangement shown in Fig. 1'7 may be adopted; in this modification girders cl2 supported by the uprights a9 are carried across the furnace, and the conveyor guide bar D7 is secured to the girders cl2, by the brackets 178', the guides D8 are also carried from the girders cl2, the conveyor canti-lever b5' to which the pendant bars B are secured, is guided by the girders bl' and b8; U10 is the chain of the conveyor. In

this arrangement the conveyor is supported independently of the walls of the furnace. The chamber in which the conveyor is located is closed in by detachable roofing portions cl3 ltting in between the girders cl2.

The arrangement of transverse flow of furnace gases described is adapted for the usual classand size of tin plate sheets, where the sheets are comparatively large and very thin.

rIhe arrangement of the fuel inlets f1 and outlets k1 may be modied; examples of the modification being illustrated in Figs. 11 and 12; for the purpose of comparison Fig. 10 is a diagrammatic View :similar to Figs. 11 and 12 and shows the arrangement illustrated in Figs. 1 to 6.

In Fig. 11 the flow of the gases is substantially as illustrated in Figs. 1 to 6 and Fig. l0, except that externally located burners f10 are employed; the burners are fed with suitable cleaned gas and air from regulable supplies, or the burner may be fed with fuel oil and air, in some cases the air supply may be heated and supplied to the burners.

In some cases each longitudinally spaced group of inlets or outlets may comprise several inlets arranged approximately in the same vertical plane, as shown in Fig. 12. On the left hand side of the figure, four inlets f1 are shown supplied with gas and air through the flues Q10 and 7'10, andion the right hand side of the figure, four inlets f1 are shown respectively supplied with gas and air from the burners Jill, the flow of gas from each of the inlets f1 being downward to the respective outlets lcl of the group.

I have referred to the openings f1 as inlets, and to fl() and fll as burners; it is to be understood that the inlets fl, the mixing chambers F and the upcasts thereto for gas and air constitute burners in the generally accepted meaning of that term.

Although the furnace is adapted to use air and washed gas the preferred method of ring the furnace is that in which raw unwashed gas is employed, the unwashed gas, of course, being mixed in the mixing chambers as shown in Fig.

1, and the washed gas being burnt in metal burners.

In the arrangement shown in Figs. 1 to 6 doors such as D4 are employed to isolate the space at the end of the cooling chamber which is connected to exhausting means so as to maintain pressure therein below the atmosphere; it is to be understood however that any suitable form of doors or equivalents for example, rollers such as C may be employed for this purpose.

The form of conveyor and mode of attachment thereto of the sheets is also well adapted for large thin sheets but any suitable form of conveyor may be employed, and Whilst the type of recuperator illustrated is well adapted for use in the furnace described, of course any other suitable form of recuperator may be employed.

The details of construction would be varied in accordance with the size and class of sheets to be heated.

Having now fully described my invention, I declare that what I claim, and desire to secure by Letters Patent, is:-

1. In a furnace for heating metal sheets, in combination:-an endless conveyor traversing the upper portion of the furnace longitudinally; means carried by the conveyor by which the sheets are detachably secured to the conveyor by their upper edges arranged in line so that they hang down vertically as theyare carried by the conveyor through the furnace; a series of longitudinally spaced inlets opening into the furnace and disposed in two sets, one on each side of the bottom of the furnace; a series of burners supplied with air and fuel and connected respectively to said inlets; a series of longitudinally spaced outlets from the furnace located at the center of the bottom of the furnace and connected to an exhaust flue; division walls respectively located between the inlets and the t outlets and extending above the ioor of the furnace; and a recess in the wall of the furnace above each inlet, said recesses tapering inwardly and upwardly to the top of the furnace.

2. In a furnace for heating metal sheets, in combinatiom-an endless conveyor traversing the top of the furnace chamber longitudinally; means carried by the conveyor by which the sheets are detachably secured to the conveyor by their upper edges arranged in line, and hang down vertically as they are carried by the comveyor through the furnace, and form a longitudinally moving partition dividing the furnace into two sections; a series of inlets, connected to a supply of heating gases, and opening directly into the furnace interior, located. one set on each side of the furnace near the bottom thereof, and adapted to direct the heating gases in two strearns to the upper part of the furnace, one stream in each of said sections, in contact with the wall thereof; and outlets for the heating gases arranged in the bottom of the furnace and located between the oppositely disposed inlets.

3. A furnace as claimed in clairn 2, in which the side walls of the furnace chamber, with which the ascending gases ina-ke Contact, are inclined inwardly towards the top of the fugnace.

4. In a furnace for treating metal sheets, in co1nbination;an endless conveyor traversing the top of the furnace chamber longitudinally; means carried by the conveyor by which the sheets are detachably secured thereto by their upper edges arranged in line; inlets, connected to a supply of heating opening directly into the furnace interior located one on each side of the furnace near the bottorn thereof; a furnace chamber having side walls sloping inwardly and upwardly frein the inlets, and a central portion of the bottom located below the level of the inlets; and outlets for the heating gas from the furnace forined in the said central portion of the bottom.

5. In a furnace for treating metal sheets, in combinationg-an endless conveyor traversing the top of the furnace longitudinally; means carried by the conveyor by which the sheets are detachably secured thereto by their upper edges arranged in line; two sets of longitudinally disposed heating gas inlets opening into the interior of the furnace and located one set at each side of the furnace near the bottoni thereof; a fuel burner for each inlet; a furnace chamber having side walls sloping inwardly from the inlets to the top of the furnace, and a central portion of the bottom which is located below the level of the inlets; an exhaust duct extending longitudinally the furnace below the said portion of the bottom; and longitudinally spaced outlets for the heating gases in the said portion of the bottom and opening into the said exhaust duct.

6. In a furnace for treating metal sheets, in ooinbinationg-an endless conveyor traversing the top of the furnace chamber longitudinally; means carried by the conveyor by which the sheets are detachably secured by their upper edges arranged in line; two sets of longitudinally spaced heating gas inlets opening into the interior of the furnace and located one set at each side of the furnace near the bottoni thereof; mixing cha. bers respectively communicating with the said inlets; a duct extending longitudinally the furnace and sup-plied with air for combustion; regulable means connecting the respective ducts to the mixing chamber; a furnace chamber having side walls sloping inwardly from the inlets to the top of the furnace, and a central portion of the bottoni located below the level of the inlets; an exhaust duct extending longitudinally the furnace below the said portion of the bottoni; and longitudinally spaced outlets for the heating gases in the said portion of the bot torn and opening into the said exhaust duct.

ERNEST GRIFFITHS.

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